Additional recovery of hydrocarbons from a petroliferous formation



1966 e. D. THOMPSON ETAL 3,233,670

ADDITIONAL RECOVERY OF HYDROCARBONS FROM A PETROLIFEROUS FORMATION FiledJuly 18, 1960 4 Sheets-Sheet 1 PRODUCING WELL OVERBURDEN CAPROCKFORMATION I4 POROUS OIL FORMATION ENTRY Io .WELL 20 PREDOMINATELYCALCIUM CARBONATE ROCK FORMATION FIG. I.

R J I ....L 1 MNEH I E OL N N T R EPTO O WMU T 1M M TD N DWO ET ERP NDMENA GAH Y B 1966 s. D. THOMPSON ETAL 3,233,670

ADDITIONAL RECOVERY OF HYDROCARBONS FROM A PETROLIFEROUS FORMATION FiledJuly 18, 1960 4 Sheets-Sheet 2 R I C P F A N OS T m K N EG NW V D m n ENH 0 .Z

FLOWING OIL REA OF COOLED GAS ZONE WATER POROUS OIL FORMATION G N ML Ul-DE OW R P x, m w n R U w; R E V L O L E W m 0 2 E O 4 I W I T E Jw mPREDOMINATELY CALCIUM CARBONATE ROCK FORMATION INVENTORS. THOMPSON,

o. SUTTLE,JR., N s. CORNEIL,

ATTORNEY.

Feb. 8, 1966 s. D. THOMPSON ETAL 3,233,670

ADDITIONAL RECOVERY OF HYDROCARBONS FROM A PETROLIFEROUS FORMATION FiledJuly 18, 1960 4 Sheets-Sheet 5 ENTRY WATER WELL INJECTION WELLOVERBURDEN CAPROCK FORMATION POROUS OIL FORMATION CAPROOK FORMATIONCONSOLIDATED FORMATION PREDOMINATELY CALCIUM CAREONATE ROCK FORMATIONINVENTORS GENE D. THOMPSON, ANDREW D. SUTTLE,JR. 4 HAMPTON G. CORNEIL,

ATTORNEY.

1966 e. D. THOMPSON ETAL 3,233,670

ADDITIONAL RECOVERY OF HYDROCARBONS FROM A PETROLIFEROUS FORMATION FlledJuly 18, 1960 4 Sheets-Sheet 4 ACCESS WELL PRODUCING WE L INJECTION WELLPLANT IIG OVERBURDEN CAPROOK FORMATION POROUS OIL FORMATION INTERMEDIATEFORMATIONS CONSOLIDATED FORMATION PREDOMINATELY CALCIUM CARBONATE ROCKFORMATION D. THOMPSON,

TON G. CORNEIL,

FIG.5. an/(gla ATTORNEY.

GENE ANDREW D. SUTTLE,JR. HAMP United States Patent 7 3,233,670ADDITIONAL RECOVERY OF HYDROCARBONS FROM A PETROLIFEROUS FORMATION GeneD. Thompson, Houston, Tex., Andrew Suttle, Jr., Jackson, Miss, andHampton G. Cornell, Baytown, Texz, assignoi's, by mesne assignments, toEsso Production Research Company, Houston, Tex., a corporation ofDelaware Filed July 18, 1960, Ser. No. 43,586 Claims. (Cl. 16611) Thisinvention relates to a method for generating gases. More particularly,the present invention relates to a method for generating a subsurfacehigh temperature gas deposit for the additional recovery of oil or gasfrom a porous Subsurface hydrocarbon bearing formation, the generationof power, etc.

.It is known that an enhanced recovery of oil can be obtained fromsubsurface porous petroliferous. formations by additional recoverytechniques wherein a gas such as carbon dioxide, normally gaseoushydrocarbons, steam, etc. or a mixture thereof are injected into theformation in order to provide a driving mechanism to cause hydrocarbonsin place to flow from an injection well toward a producing well (see,for example, W'horton et al., US. Patent No. 2,623,596). l

A serious problem is encountered with additional recovery operationswith respect to the acquisition and injcction of the large quantities ofthe inert gases or hot gases or both that are required for the increasedrecovery operations. The cost of generating such gases above ground aresignificant and, likewise, tl 1e cost of pumping equipment and injectionwells for in ecting the gases into the petroliferous formation 18significant.

The present invention is directed to a method for the subsurfacegeneration of large quantities of inert gases and to the utilization ofsuch gases for the increased recovery of hydrocarbons from apetroliferous subsurface formation. The present invention isparticularly useful for increased recovery operations wherein thesubsurface 'petroliferous formation is associated with a geologicalformation containing a predominant amount of a carbonate rock.

Briefly, an access well is drilled from the surface of the earth intothe carbonate rock formation. After suitable prefracturing of thepetroliferous formation "(If necessary) a nuclear fusion device or anuclear fission device is spotted in the access well in the carbonaterock formation. The access well is closed and the nuclear device isactuated, whereby a number of events occur.

During the actuation step, a substantial void 18 formed which issurfaced with a shell of molten rock containing a predominant amount ofthe radioactive entities formed by the actuation. Collapse of the roofwill form a chimney above the spherical void to thereby provide a rubblefilled cavity. The high temperatures generated by the actuation willdecompose large and significant quantities of the carbonate rock intometal oxides such as calcium oxide, magnesium oxide, etc. and carbondioxide, and may also cause reactions to occur with respect to suchwater and organic matter as may be present.

Alkaline earth metal oxides such as magnesium or calcium oxide form amagmatic type of eutectic with alkaline earth metal carbonates attemperatures in excess of about 1200 C. and this magma seals off voidsor cracks or other permeations in the carbonate rock formation. As aconsequence, high temperature carbon dioxide is provided for any desiredpurpose (e.g., a gas type of drive) together with a body of confinedhigh temperature magma. As will be hereinafter described, the carbondioxide that is formed in this manner may be used for an increased oilrecovery operation and simultaneously or subsequently, the thermalenergy of the magma may be utilized to generate gases for usefulpurposes such as power generation, supplemental additional hydrocarbonrecovery operation, etc. The resulting gases which contact oil orcondensate will also swell the fluids and improve mobility.

The invention will be further described in the accompanying drawingsherein.

FIGURE 1 is a schematic evaluation view in section illustrating the onemode of increased recovery which may be practiced in accordance with thepresent invention;

FIGURE 2 is an evaluational fragmentary view of a portion of apetroliferous formation illustrating the manner in which the multi-typegas drive is accomplished in accordance with the present invention; and

FIGURES 3 to 5 are schematic evaluational views in section illustratingmodified methods of practicing the present invention.

Turning now to FIGURE 1, there is shown a sectional view of a geologicsequence extending from the surface of the earth 10 through anoverburdened formation or formations 12 and through an oil imperviouscaip rock formation 14 such as shale, compacted sandstone, etc.overlying a porous dil formation 16. Formation 16 is representative ofthe various type of petroliferous oil formations which are encounteredbelow the ground such as porous sandstone formations, porous carbonaterock, limestone (e.g., submerged coral reefs), etc.

There is also shown a carbonate rock formation 18 as a host formationfor the nuclear device and it may be characterized as a formation whichcontains a significant amount (e.g., 30 to weight percent) of acarbonate rock. Representative formations of this nature includedolomite formations, limestone formations, chalk formations, etc. andrelated formations containing significant quantities of carbonateminerals (e.g., calcite, dolomite, magnesite, aragonite, etc.).

' In order to initiate the additional recovery operation of the presentinvention, an access well 20 and a recovery well 22 are drilled from thesurface of the earth. It will be understood that it will normally bepreferred to utilize a plurality of existing or newly drilled producingwells 22 which are spaced about the access well 2th in any normalinjecting-producing pattern (e.g., a 5-spot pattern surrounded Withmultiple rows of recovery Wells).

The present invention finds particular utility with respect to highlycompacted petroliferous formations which are comparatively impermeableto injected fluids, since the permeability of such formations can beimproved by prefracturing, by seismic fracturing caused by actuation ofthe nuclear device or by post-fracturing with the hot, high pressuregases formed by the actuation.

Accordingly, if the porous oil formation 16 is a coniparativelyimpermeable formation of this character, the access Well 20 is initiallydrilled from the surface into the porous oil formation 16. Next, theformation is fractured by any suitable fracturing technique, such as themethod disclosed in Brown et al. U.S. Patent No. 2,779,735 if aprefracturing technique is to be employed. The prefracturing step willresult in the opening of fractures (e.g., sand propped fractures) in theformation.

After completion of the. preliminary fracturing step, if such a step isnecessary, the access well 20 is further drilled into the underlyingcarbonate rock formation, which in the embodiment of FIG. 1, directlyunderlies the porous oil formation.

The extent to which the access well 20 is drilled into the carbonaterock formation 18 will be dependent upon a number of factors.

Firstly, the size of the nuclear device is predetermined.

The size of a nuclear device is normally expressed in terms of theenergy release which is obtained by actuation of the nuclear device.Thus, a nuclear device liberating an amount of energy equal to theamount of energy obtained by turning 1000 tons (1 kiloton) of TNT(trinitrotoluene) it is conventionally defined as a 1 kiloton device andis defined as ore which releases 10 cal.

It is desirable to confine the explosive force of the nuclear devicebelow the surface of the ground and, therefore, the device should beactuated at a depth from the surface of the earth 10 which is at leastsufiicient to satisfy the equation:

D=KE

wherein D is the depth in feet;

K is a constant having a value within the range of 1000 E is the energyof the nuclear device in terms of megaton equivalents of TNT; and

n is an exponent having a value between 0.1 and 0.5.

Preferably, K is about 3000, and n is about 0.3.

The size of the cavern that initially will be formed upon actuation ofthe nuclear device is dependent upon a number of factors including theporosity of the formation and the resistance of the formation to ruptureor fracture. Generally speaking, the radius of the cavern may beestimated from the formula:

R=Radius in Meters E :Energy of device in kilotons P=Pressure,atmospheres Also, it is desirable that the chimney formed by collapse ofthe roof of the initial spherical cavern be of a height such that thecap rock formation 14 above the petroliferous formation 16 is notcompletely pierced. The height and shape of the chimney will bedetermined, of course, by the nature of the carbonate rock formation andthe formations overlying such carbonate rock formations.

As has been indicated, the nuclear device to be utilized is a nuclearfission device or a nuclear fusion device.

The nuclear device to be utilized in accordance with the presentinvention may be defined as a nuclear device which will releasesubstantially all its available energy within not more than about 60minutes after the establishment of criticality by changes involvingexoergic transformation. Normally, the energy will be released withinless than 1 second.

The fuel components of the nuclear device will include nuclear fissioncomponents, nuclear fusion components, or both. The fuel componentshould preferably consume comparatively low cost and abundant isotopes.A table of useful fusion fuel reactants, the fusion products resultingtherefrom and the energy release obtainable are listed in the followingtable:

TABLE I Useful nuclear reactions Reaction: Q, mev. (1) D (d,n)l-le 3.25(2) D (d,p)T 4.08 (3) T (d,n)He 17.6 (4) He (d,p)He 18.3 (5) Li (d,a)He22.4 (6) Li"(p, x)He 17.3

Further examples of suitable nuclear reactions which may be employed,together with the energy obtainable therefrom, are set forth in TableII.

' 4 TABLE II Selected exoergic reactions of low Z isotope Reaction: Q,mev. (1) p (I1,'y)D 223010.005 (2) D (I1,'y)T 6.2510008 (3) D (p,'y)He55010.03 (4) D (d,p)T 403010.006 (5) D (d,n)He 326510009 (6) T (p,'y)He2 19.710.04 (7) T (d,n)He 2 1757810030 (8) He (t,p)He 11.181007 (9) He(n,p)T 0.76610.010 (10) He (d,p)He 18.451017 (11) He (d,'-, )Li 16310.2(12) He (He ,p)Li 10.861015 (13) Li (n,a)T 4.80410.022 (14) Ll (P,oc)H402310003 (15) Li (d,ot)I-Ie 2239610012. (16) Li (d,p)Li 502810003 (17)Li (d,n)Be" 3.401005 (18) Li (t,d)Li' 0.98210.007 (19) Li (He ,p)Be16.601? (20) Li (p,a)He 1734610010 (21) Li"'(p;y)l3e 17.1102 (22) Li'(d,a)He 14210.1 (23) Li (d,n)Be 15.0101 24) Li"(t,a)I-Ie 91910.03 (25)B6 2oc 009410.001

1 Preferred reactions.

2 Reactions giving the most favorable results.

The fusion reaction is normally triggered. by a critical mass of afissile material such as U U Pu which is initially of a non-criticalconfiguration and which is brought into a condition of critically whenthe device is to be fired in order to initiate the exoergictransformation.

In some situations it is desirable to obtain the desired amount ofenergy solely from nuclear fission reactions. However, for the greatesteconomy, it is preferable to employ nuclear fusion reactions.Preferably, the nuclear device to be utilized is a nuclear fusion devicehaving energy equivalent within the range of about to kilotons of TNT.

The general sequence of events that will transpire on actuation of thenuclear device is similar to that described in U.C.R.L., publication5124 of the University of California Laurence Radiation Laboratoryentitled The Underground Detonation of September 19, 1957-RanierOperation Plumb Bob dated February 4, 1958.

Thus, a cavern will be formed initially due to expansion of the fireball. The surface of the cavity will be defined by a zone of heated rockand extending outwardly from this zone will be a spherical zone ofcrushed rock. Thereafter, collapse of part of the surface of the upperpart of the cavern will occur whereby a chimney will be formed extendingupwardly from the zone of actuation. Thus, in FIG. 1, there is shown atthe end of the actuation step, a lower zone A of crushed rock, anintermediate zone B of fused rock derived from the surface of theinitial cavity. This zone will contain a major portion of the bombdebris. Extending upwardly of zone B is a zone C of crushed rock andrubble derived from the chimney 21 extending upwardly into the porousoil formation 16.

Since temperatures in excess of 3000 C. are generated by actuation,large quantities of the carbonate rock will be decomposed into carbondioxide and metal oxides including a substantial amount of calcium andmagnesium oxide. Calcium oxides melt at a temperature of about 2570 C.and form a magmatic eutectic with solid calcium oxide at a temperatureof about 1200 C. In similar fashion, magma is formed from the otheralkaline earth metal carbonates. This highly viscose magma is thereforeformed in the zone by high temperature contact of the molten alkalineearth metal oxide (e.g., magnesium or surface 30.

calcium oxide) with solid alkaline earth metal oxides (e.g., calcium ormagnesium oxide). As a consequence, any fissures or fractures or othervoids about the cavern which are not self-sealing are effectively sealedby this magma. The same effect occurs in the portion of the chimney 21extending through the carbonate rock formation because hot high pressurecarbon dioxide and gases associated therewith will cause melting andmagmatic jeutectic formation to occur about the surface of the chimney.

As a consequence, the high temperature, high pressure carbonfdioxide ismaintained within the void caused by actuation of the nuclear device,and it is not difused throughout the carbonate rock formation throughfissures and cracks. As a further consequence, the thermal energyreleased by the nuclear device is retained adjacent the situs ofactuation because the magmatic eutectic prevents the entry of formationfluids such as water, which would otherwise tend to. rapidly dissipatethe heat.

The thermal energy that is retained in this fashion may be used fora'number of purposes, as hereinafter described.

- In FIG. la chimney 21 is shown'as extending upwardly into the porousformation16. A magmatic eutectic lwill coat the, fractures of the porousoil formation 16 and, as a consequence, the hot carbon dioxide willintrude into the formation 16 through natural fissures, fissures causedby .the detonation, fissures formed by prefracturing or combinationsthereof to initiate additional recovery operations. In addition, thepressure and heat of the hot carbon dioxide may. be suflicient to causepost-fracturing of the formation, or the extension or furtherdevelopment of existing fraction patterns.

, Turning now to. FIG. 2, there is schematically shown a fractured,exposedsurface 30 of the petroliferous forma- -tiou.16.into which hotcarbondioxide flows. The hot 'carbon. dioxide will react withpetroliferous materials immediately adjacent the surface 30 to decomposethe same .int0;.hot gases including hydrogen, carbon monoxide, etc. .Asa consequence of this reaction, and of the need for heating theformation, the initially introduced carbon dioxide will be formed into abank of relatively cool gases comprising carbon dioxide, carbonmonoxide, hydrogen, etc.1 As further; quantities of carbon. dioxideintrude the Iformation the cool gases will flow further. into theformation to thereby provide a driving bank for displacing flowablepetroliferous fluids in the zone 16 whereby such caused'to flow by abank of cool gas as defined above, which is shown in FIG. 2 as zone II.Adjacent zone II is'a zone III which may be characterized as a heatreac- Rtionzone. Within this zone, nonflowable petroliferous fluids areheated to temperatures in excess of about 400 1 C. by the hot carbondioxide, and, as a result, chemical 'interrea-ctions occur between theresidual petroliferous fluids and the hot carbon dioxide whereby thedriving bank Qfrelatively cool gasis formed. Hot gas is introduced intothe formation zone 16 in zone IV, adjacent exposed A Stated differently,zone IV is a heated zone substantially free from petroliferous fluidscontaining predominantly thehot gas introduced i n the surface 30. s

Zone IIIcomprises, as indicated, a reaction zone wherein the hotgasreacts with the residual hydrocarbons present in the formation. Asaconsequence, additional gases are formed which have a lowertemperature,whereby a bank of cooled gas is formed which drives the flowablepetroliferous fluids of,zone I toward producing wells.

After the passage of a suitable period of time, pressure equilibriumwill be reached due to the flow of carbon dioxide into the porousformation 16. Prior to or subsemay terminate at its quent to this time,additional quantities of hot gas or steam may be provided, as shownschematically in FIG. 3.

Turning now to FIG. 3, an injection well 40 is drilled from the surfaceto a point in the cavern formed by the actuation of the nuclear deviceand entry into the cavern is established either by drilling the wellthereinto or by stopping the well a short distance from the surface andthen fracturing the formation in order to provide entrance.

A liquid which is capable of reacting with the hot magma in the cavernis then injected in the well 40.

For example, the liquid may be a low quality, heavy residual crude oilfraction which will be decomposed in the cavern into hydrogen and lighthydrocarbon gases such as methane, etc. and residual carbon.Decomposition of the low quality hydrocarbon will cause additionalquantities of gas to be generated which will flow into the porous oilfraction 16 in the manner indicated above.

As an alternate or supplementary measure, water may be injected throughthe well 40. The thus injected water will slake the lime in the cavernand significant quantities a predominantly carbonate rock formation 50underlying an impervious consolidated formation 52 which, in turnunderlies a porous oil formation 54. Porous oil formation 54 will, inturn underlie a cap rock formation 56 which, in turn, will underlieoverburden 58.

In this situation, an entry well 60 may be drilled from the surface intothe carbonate rock formation 52 in the manner described above withrespect to FIG. 1 and a nuclear device may be spotted in the carbonaterock formation 50 and actuated therein in the manner described abovewith respect to FIG. 1 whereby there is formed a subsurface'cavern 62containing high temperature, high pressure carbon dioxide and surfacedwith a glass such as a magmatic eutectic of calcium oxide. The cavern 62may thus contain a lower zone A of crushed rock, an intermediate zone Bof fused rock derived from the surface of the initial cavity and a zoneC composed of crushed rock and rubble formed from a chimney 64 extendingupwardly from the zone of actuation. The chimney 64 may extend upwardlyfrom the host rock formation 50 into consolidated formation 52 or,alternately,

upper end within the host rock formation (not shown). I

In order to produce oil from porous oil formation 54 overlying the hostrockformation 50, there is provided ,a producing well 66 or a pluralityof such producing Wells chimney 64 of the cavern 62 and the well isclosed at the surface with a suitable high pressure packing Christmastree schematically shown by the reference numeral 70. 'As a consequence,hot carbon dioxide will flow from the chimney 64 thorugh the well 68 upto porous formation 54 and will thereafter enter into formation 54 topromote additional recovery operations in the manner described abovewith reference to FIGURE 2.

When the supply of carbon dioxide is substantially exhausted or at anyotherdesired time, an additional in jection well 72 may be drilled fromthe surface into the chimney 64. Water may be injected thereinto for theproduction of steam within the cavern, such steam flowing upwardlythrough access Well 68 into producing formation 54-; to further assistin additional recovery operations. Alternately, a liquid which iscapable of reacting with the hot magma in the cavern is injected throughinjection well 72 such as a petroleumhydrocarbon (e.g., heavy residualcrude oil) which is decomposed thermally into hydrogen, lighthydrocarbon gases and residual carbon. The hot gases in this situationwill flow upwardly through the access well 68 and into porous oilformation 54 to promote additional recovery operations. I

It will be understood that in the practice of the present invention itwill normally be desirable to utilize wellhead equipment which iscapable of preventing blowouts due to the high pressure of the carbondioxide or other gases generated in the subsurface cavern. Suitablewellhead equipment for this purpose is disclosed, for example on page4155 of the Composite Catalog of Oil Field and Pipe Line Equipment forthe Year 1957.

An alternate method, as shown in FIG. 5, is to produce gases from thecavern to the surface and to utilize and inject the gases into injectionwells in a hydrocarbon bearing formation adjacent to but not directlycommunicating with the cavern.

Turning now to FIG. 5, there is shown a predominantly carbonate rockformation 100 underlying an impervious consolidated formation 102 which,in turn, underlies intermediate formation 104 and a porous oil formation106. A caprock formation 1118 overlies oil formation 106 which formation108, in turn, is overlain by overburden 110.

In FIG. 5, there is shown a cavern in the carbonate rock formation 100formed, for example, in the manner described above with respect to FIG.1 and comprising a lower zone A" of crushed rock, an intermediate zone Bof fused rock derived from the surface of the initial cavity which Zonecontains a major portion of the bomb debris. Extending upward of zone B"is a zone C" of crushed rock and rubble derived from the chimney 21"extending upwardly (e.g., into consolidated formation 102). In FIG.there is also schematically shown the initial entry well 60' used forspotting of a nuclear device in the carbonate rock formation 100, asdescribed in connection with FIG. 1.

In accordance with the embodiment of the present invention shown in FIG.5, an access well 112 containing suitable surface control equipment 114is drilled from the surface into the carbonate rock formation.Communication between the cavern and the entry well 112 is establishedin any suitable manner. For example, the well 112 may be terminated at apoint adjacent to the cavern and, through the use of suitablefractioning techniques, such as those conventionally employed for thefracturing of hydrocarbon formations, fissures and cracks may be openedfrom the cavern through the carbonated rock formation and into theaccess well 112.

In addition, an injection well 115 is drilled into porous oil formation106 and at least one producing well 116 is also drilled in the oilformation 106. The access well 112 is interconnected with the injectionwell 115 by suitable means such as how line 118 leading from access well112 to a plant 120 which may be a simple manifolding station or a plantfor at least partial utilization of the gases from the cavern forpurposes such as electricity generation, heating, etc. From plant 120 aline 122 is provide which leads to injection well 115.

As a consequence, carbon dioxide from the cavern may be withdrawn fromthe well 112 and transported by way of surface line 118, plant 120 andsurface line 122 to injection well 115. The carbon dioxide may beintroduced into the porous oil formation 106 to initiate or further theprogress of additional recovery operation being conducted in porous oilformation 106. In this case, of course, the additional production isachieved by way of a producing well 116, or, more preferably, aplurality of such producing wells spotted around the injection well 115.

As in the previous embodiments, additional quantities of gas may beprovided by drilling an injection well 124 to a point adjacent thecavern, by communicating the injection well 124 with the cavern in anysuitable manner (e.g., by fracturing step for the purpose of openingfissures and cracks to formation 102 intermediate the cavern and well104). After this has been done, a liquid such as water or a hydrocarbonmay be introduced into the cavern by way of an injection well 124 toprovide additional quantities of gas such as steam or mixtures ofhydrogen or light hydrocarbons. The additional gases may then bewithdrawn from the cavern by way of well 112 and charged to porous oilformation 106 through the injection well in the described manner.

Having thus described our invention, what is claimed 1. A method for theadditional recovery of petroliferous hydrocarbons from a petroliferousformation containing at producing Well and lying adjacent apredominantly calcium carbonate formation which comprises the steps ofspotting a nuclear explosive device in said calcium carbonate rockformation and actuating said device to thereby provide a caverncontaining hot magma and high temperature carbon dioxide and introducingsaid carbon dioxide into said porous oil formation to drivepetroliferous hydrocarbons in said porous oil formation toward saidproducing well and producing said petroliferous hydrocarbons andgenerating additional gases in said ca'v'ern for said additionalrecovery operations by contacting the hot magma in said cavern withwater to produce steam and by introducing said steam intosaidpetroliferous formation.

2. A method for the additional recovery of petroliferous hydrocarbonsfrom a petroliferous formation containing a producing well and lyingadjacent a predominantly calcium carbonate formation which comprises thesteps of spotting a nuclear explosive device in said calcium carbonaterock formation and actuating said device to thereby provide a caverncontaining hot magma and high temperature carbon dioxide and introducingsaid carbon dioxide into said porous oil formation to drivepetroliferous hydrocarbons in said porous oil formation toward saidproducing well and producing said petroliferous hydrocarbons andgenerating additional gases in said cavern by contacting the hot magmawith a heavy residual crude oil fraction to produce hydrogen and lighthydrocarbon gases.

3. A method which comprises drilling a first well from the surface ofthe earth through a petroliferous formation into an underlying formationcontaining a predominant amount of calcium carbonate and drilling asecond Well from the surface of the earth into said petroliferousformation and laterally spaced from said first well, spotting a nuclearexplosive device in said first well in the portion thereof penetratingsaid calcium rock formation .and activating said device to therebyprovide a cavern containing high temperature carbon dioxide and hotmagma, said nuclear explosive device 'being spotted with respect to saidcalcium carbonate rock formation and said petroliferous formation in amanner such that said cavern extends upwardly from said calciumcarbonate rock formation into said petroliferous formation whereby saidhigh temperature carbon dioxide will spontaneously flow into saidpetroliferous formation to drive petroliferous hydrocarbons therein tosaid second well and producing said petroliferous hydrocarbons andintroducing water into said cavern after pressure equilibrium betweensaid cavern and said petroliferous formation has been established inorder to generate high temperature steam under pressure suflicient topermit said steam to spontaneously penetrate said petroliferousformation to drive additional quantities of petroliferous hydrocarbonscontained therein toward said producing well and wherein said additionalpetroliferous hydrocarbons are produced.

4. A method which comprises drilling a first well from the surface ofthe earth through a petroliferous formation into an underlying formationcontaining a predominant amount of calcium carbonate and drilling asecond well from the surface of the earth into said petroliferousformation and laterally spaced from said first well, spotting a nuclearexplosive device in said first well in the portion thereof penetratingsaid calcium rock formation and activating said device to therebyprovide a cavern containing high temperature carbon dioxide and hotmagma, said nuclear explosive device being spotted with respect to saidcalcium carbonate rock formation and said petroliferous formation in amanner such that said cavern extends upwardly from said calciumcarbonate rock formation into said petroliferous formation whereby saidhigh temperature carbon dioxide will spontaneously flow into saidpetroliferous format-ion to drive petroliferous hydrocarbons therein tosaid second well and producing said petroliferous hydrocarbons andintroducing residual oil into said cavern after pressure equilibriumbetween said cavern and said petroliferous formation has beenestablished in order to generate high temperature hydrogen and lighthydrocarbon gases under pressure sufficient to permit said hydrogen andlight hydrocarbon gases to spontaneously penetrate said petroliferousformation to drive additional quantities of petroliferous hydrocarbonscontained therein toward said producing Well and wherein said additionalpetroliferous hydrocarbons are produced.

5. A method for the additional recovery of petroliferous fluids from aporous oil formation (underlying or overlying and) remotely spaced froma predominantly calcium carbonate rock formation which comprises thesteps of activating a nuclear explosive device in a calcium carbonaterock formation to thereby provide a cavern containing hot magma and hightemperature carbon dioxide, drilling a well through said petroliferousformation, establishing fluid communication between said cavern and saidwell and flowing said hot carbon dioxide from said cavern through saidwell into said petroliferous formation to drive petroliferoushydrocarbons contained therein toward a producing well and producingsaid petroliferous hydrocarbons and introducing Water into said cavernafter pressure equilibrium between said cavern and said petroliferousformation has been established in order to generate high temperaturesteam under pressure suflicient to permit said steam to be flaredthrough said well to penetrate said petroliferous formation to driveadditional quantities of petroliferous hydrocarbons contained thereintoward said producing well and herein said additional petroliferoushydrocarbons are produced.

References Cited by the Examiner Uren, Lesterz' Petroleum ProductionEngineering, 4th edition, McGraW-Hill Book Co., 1956, pp. 14-25.

UCRL-S 124, Feb. 4, 1958, pp. 3, 27.

UCRL-5026, University of California Radiation Laboratory, Non MilitaryUses of Atomic Energy, June 12, 1958, pp. 7-9.

The Washington Post and Times Herald, Nov. 12, 1958, p. B12.

Non-Military Uses of Nuclear Explosives. American, pp. 199, 29-35 (1958)Dec.

UCRL-5458, University of California Radiation laboratory MineralResources Development by the Use of Nuclear Explosives, Feb. 5, 1959,pp. 13-15.

UCRL-5678, Plowshare Series, Water Resources, Mining, Chemical,Petroleum, May 15, 1959, pp. 74-101.

UCRL-S 840, University of California Radiation Laboratory, industrialand Scientific, Applications of Nuclear Weapons, January 19, 1960, pp.9, 10, 11, 28.

Scientific REUBEN EPSTEIN, Primary Examiner.

CARL D. QUARFORTH, LEON D. ROSDOL, ROGER L. CAMPBELL, Examiners.

1. A METHOD FOR THE ADDITONAL RECOVERY OF PETROLIFEROUS HYDROCARBONSFROM A PETROLIFEROUS FORMATION CONTAINING A PRODUCING WELL AND LYINGADJACENT A PREDOMINANTLY CALCIUM CARBONATE FORMATION WHICH COMPRISES THESTEPS OF SPOTTING A NUCLEAR EXPLOSIVE DEVICE IN SAID CALCIUM CARBONATEROCK FORMATION AND ACTUATING SAID DEVICE TO THEREBY PROVIDE A CAVERNCONTAINING HOT MAGMA AND HIGH TEMPERATURE CARBON DIOXIDE AND INTRODUCINGSAID CARBON DIOXIDE INTO SAID POROUS OIL FORMATION TO DRIVEPETROLIFEROUS HYDROCARBONS IN SAID POROUS OIL FORMATION TOWARD SAIDPRODUCTING WELL PRODUCING SAID PETROLIFEROUS HYDROCARBONS AND GENERATINGADDITIONAL GASES IN SAID CAVERN FOR SAID ADDITIONAL RECOVERY OPERATIONSBY CONTACTING THE HOT MAGMA IN SAID CAVERN WITH WATER TO PRODUCE STEAMAND BY INTRODUCING SAID STEAM INTO SAID PETROLIFEROUS FORMATION.